Patients with geleophysic dysplasia are not always geleophysic

Secreted ADAMTS-like proteins as regulators of connective tissue function

The extracellular matrix (ECM) determines functional properties of connective tissues through structural components, such as collagens, elastic fibers, or proteoglycans. The ECM also instructs cell behavior through regulatory proteins, including proteases, growth factors, and matricellular proteins, which can be soluble or tethered to ECM scaffolds. The secreted a disintegrin and metalloproteinase with thrombospondin type 1 repeats/motifs-like (ADAMTSL) proteins constitute a family of regulatory ECM proteins that are related to ADAMTS proteases but lack their protease domains. In mammals, the ADAMTSL protein family comprises seven members, ADAMTSL1-6 and papilin. ADAMTSL orthologs are also present in the worm, Caenorhabditis elegans, and the fruit fly, Drosophila melanogaster. Like other matricellular proteins, ADAMTSL expression is characterized by tight spatiotemporal regulation during embryonic development and early postnatal growth and by cell type- and tissue-specific functional pleiotropy. Although largely quiescent during adult tissue homeostasis, reexpression of ADAMTSL proteins is frequently observed in the context of physiological and pathological tissue remodeling and during regeneration and repair after injury. The diverse functions of ADAMTSL proteins are further evident from disorders caused by mutations in individual ADAMTSL proteins, which can affect multiple organ systems. In addition, genome-wide association studies (GWAS) have linked single nucleotide polymorphisms (SNPs) in ADAMTSL genes to complex traits, such as lung function, asthma, height, body mass, fibrosis, or schizophrenia. In this review, we summarize the current knowledge about individual members of the ADAMTSL protein family and highlight recent mechanistic studies that began to elucidate their diverse functions.

Geleophysic dysplasia: novel missense variants and insights into ADAMTSL2 intracellular trafficking

Geleophysic dysplasia (GPHYSD1, MIM231050; GPHYSD2, MIM614185; GPHYSD3, MIM617809) is an autosomal disorder characterized by short-limb dwarfism, brachydactyly, cardiac valvular disease, and laryngotracheal stenosis. Mutations in ADAMTSL2, FBN1, and LTBP3 genes are responsible for this condition. We found that three previously described cases of GPHYSD diagnosed clinically were homozygote or compound heterozygotes for five ADAMTSL2 variants, four of which not being previously reported. By electron microscopy, skin fibroblasts available in one case homozygote for an ADAMTSL2 variant showed a defective intracellular localization of mutant ADAMTSL2 protein that did not accumulate within lysosome-like intra-cytoplasmic inclusions. Moreover, this mutant ADAMTSL2 protein was less secreted in medium and resulted in increased SMAD2 phosphorylation in transfected HEK293 cells.

Limb- and tendon-specific Adamtsl2 deletion identifies a role for ADAMTSL2 in tendon growth in a mouse model for geleophysic dysplasia

Geleophysic dysplasia is a rare, frequently lethal condition characterized by severe short stature with progressive joint contractures, cardiac, pulmonary, and skin anomalies. Geleophysic dysplasia results from dominant fibrillin-1 (FBN1) or recessive ADAMTSL2 mutations, suggesting a functional link between ADAMTSL2 and fibrillin microfibrils. Mice lacking ADAMTSL2 die at birth, which has precluded analysis of postnatal limb development and mechanisms underlying the skeletal anomalies of geleophysic dysplasia. Here, detailed expression analysis of Adamtsl2 using an intragenic lacZ reporter shows strong Adamtsl2 expression in limb tendons. Expression in developing and growing bones is present in regions that are destined to become articular cartilage but is absent in growth plate cartilage. Consistent with strong tendon expression, Adamtsl2 conditional deletion in limb mesenchyme using Prx1-Cre led to tendon anomalies, albeit with normal collagen fibrils, and distal limb shortening, providing a mouse model for geleophysic dysplasia. Unexpectedly, conditional Adamtsl2 deletion using Scx-Cre, a tendon-specific Cre-deleter strain, which does not delete in cartilage, also impaired skeletal growth. Recombinant ADAMTSL2 is shown here to colocalize with fibrillin microfibrils in vitro, and enhanced staining of fibrillin-1 microfibrils was observed in Prx1-Cre Adamtsl2 tendons. The findings show that ADAMTSL2 specifically regulates microfibril assembly in tendons and that proper microfibril composition in tendons is necessary for tendon growth. We speculate that reduced bone growth in geleophysic dysplasia may result from external tethering by short tendons rather than intrinsic growth plate anomalies. Taken together with previous work, we suggest that GD results from abnormal microfibril assembly in tissues, and that ADAMTSL2 may limit the assembly of fibrillin microfibrils.

Cardiac involvement in geleophysic dysplasia in three siblings of a Saudi family

Geleophysic dysplasia is an extremely rare acromelic skeletal dysplasia resembling lysosomal storage disease. It is characterised by characteristic facial phenotype, short stature, micromelia, joint contracture, and early cardiac valvular involvement. It has been described worldwide in <40 patients. Herein, we describe the cardiac features in three Saudi sisters with proved autosomal recessive geleophysic dysplasia who showed different levels of severity of their cardiac involvement.

Novel mutations in geleophysic dysplasia type 1

Geleophysic dysplasia (GD) is a rare genetic disorder characterized by acromelic dysplasia. Geleophysic dysplasia type 1 (MIM 231050) is autosomal recessive and is caused by homozygous or compound heterozygous mutation in the ADAMTSL2 (a disintegrin and metalloproteinase with thrombosponding repeats-like 2) gene. Geleophysic dysplasia type 2 (MIM 614185) is autosomal dominant and is caused by heterozygous mutation in the fibrillin 1 (FBN1) gene. Here, we present the clinical and histopathologic findings in a child with GD with newly identified ADAMTSL2 mutations. The 1st mutation was probably a pathogenic one, c.[1934G>A] p.[Arg645His], located in exon 13; the 2nd, in intron 8, was probably changing a splice site. While the light and electron microscopic findings were similar to those previously described, hydrocephalus due to aqueductal stenosis might be a new associated finding in these patients. This child with these 2 novel mutations also had an aggressive clinical course with early-onset progressive cardiac valvular disease.

Clinical and morphological phenotype of geleophysic dysplasia

Geleophysic dysplasia (GD) is a rare, recessively inherited lysosomal storage disorder of unknown origin with a progressive course. A 9-year-old Turkish boy born to consanguineous parents with findings typical of GD is reported. Cardiac abnormalities included mitral and aortic stenosis with aortic insufficiency. There was persistent hypo-uricacidaemia, severe pulmonary hypertension and tricuspid insufficiency. He required aortic and mitral valve replacement but, unfortunately, died of a severe pulmonary infection in the post-operative period. The condition has to be differentiated from lysosomal storage disorders such as mucopolysaccharidosis.

Natural history of cardiac involvement in geleophysic dysplasia

Geleophysic dysplasia is an autosomal recessive short-limbed, dysmorphic syndrome. The condition is frequently associated with cardiac valvular disease, which may result in secondary hypertrophy and cardiac failure. We describe two distantly related Pakistani children with classical features of geleophysic dysplasia. Pulmonary stenosis was recognized in both within a few months of birth. The younger child shows no signs of cardiac decompensation at the age of 7 years whilst her older cousin has developed a significant pulmonary gradient requiring surgical intervention in the second decade of life. The natural history of his disorder highlights that the cardiac involvement seen in apparently stable forms of geleophysic dysplasia is frequently progressive.